The receiver of the base station needs to support various application scenarios simultaneously, for example, support Tower Amplification (TA) application, application of interlink connection, and main-diversity dual-path application. In order to support the applications simultaneously, a front end of the receiver needs to include modules supporting various applications, and the modules need to match one another, so that the number of the modules on the front end of the receiver is large, and structure of the receiver is complex.
TA in the TA application generally refers to a Low Noise Amplifier (LNA) installed on top of the tower which resides closely behind a receiving antenna. The TA is capable of amplifying a received signal by approximately 12 Decibels (dB) before the received signal enters the receiver, so as to enhance quality of uplink signal, improve the reliability and the voice quality of calls, and expand the cell coverage area. That is, the signals entering the receiver have different signal ranges according to whether the TA exists or according to different gains of the TA. In the prior art, the conventional dual-path receiver generally adopts link architecture as shown in FIG. 1, which adopts a mode of combining separated devices to implement gain control and satisfy interlink connection requirements. As shown in FIG. 1, in order to support the TA application, a Digital Step Attenuator (DSA) is disposed at a main path, at a diversity path, and on the most front end of an input port of the receiver each. Because the signals entering the receiver have the different signal ranges according to whether the TA exists or according to different gains of the TA, the following LNA cannot bear such a large range of signal, a DSA needs to be added at the most pre-stage of the input port. The DSA correspondingly performs attenuation according to whether the TA exists in the front end of the receiver or according to the gain of the TA, so that the voltage of the signals that reach the LNA at the post-stage is maintained at a fixed range, so as to ensure the normal operation of the entire receiver. In order to support interlink connection, the main path of the receiver achieves a function of dividing a path of signal into two paths of signals for output through a power divider (PD), while the diversity path achieves a function of combining the paths of signals into one path of signal through a switch (SW). FIG. 2 is a schematic circuit diagram of a main path of a receiver. As shown in FIG. 2, after the signal enters the main path, the main path implements the adjustment of input voltage under different configurations through a DSA, and output two paths of signals through a PD after an LNA, and an amplifier (AMP) after the PD is used to provide gains from a radio frequency input port to a radio frequency output port 1.
During the implementation of various applications by the receiver, the inventor finds that the prior art at least has the following problems. Insertion loss of the DSA is large, which directly deteriorates noise coefficients of modules on the front end of the receiver, and has great influences on the gain coefficients of the circuit. Moreover, the influence of the insertion loss of the PD and SW on the post-stage of the LNA cannot be ignored. Therefore, in order to ensure a noise-to-signal ratio of the entire receiver, the LNA should have very low noise, high gain, and good linearity. Thus, in order to ensure performance of the application modules, matching of the modules, and the performance of the receiver, the level of the noise, the gain, and the linearity of the modules are high, increasing the design difficulty.